1. Field of the Invention
The present invention relates to network switching and switch fabrics. More particularly, the present invention relates to a system and method for using standard Ethernet switches or switched Ethernet networks as switch fabrics.
2. Description of the Related Art
A network switch is a device that provides a switching function (i.e., determines a physical path) in a data communications network. Switching involves transferring information, such as data packets or frames, among entities of the network. Typically, a switch is a computer having a plurality of circuit cards coupled to a backplane. In the switching art, the circuit cards are typically called “blades.” The blades are interconnected by a “switch fabric.” Each blade includes a number of physical ports that couple the switch to the other network entities over various types of media, such as Ethernet, FDDI (Fiber Distributed Data Interface), or token ring connections. A network entity includes any device that transmits and/or receives data packets over such media.
The switching function provided by the switch typically includes receiving data at a source port from a network entity and transferring the data to a destination port. The source and destination ports may be located on the same or different blades. In the case of “local” switching, the source and destination ports are on the same blade. Otherwise, the source and destination ports are on different blades and switching requires that the data be transferred through the switch fabric from the source blade to the destination blade. In some cases, the data may be provided to a plurality of destination ports of the switch. This is known as a multicast data transfer.
Switches operate by examining the header information that accompanies data in the data frame. Various types of header information are defined by networking standards bodies such as the IEEE and IETF. The canonical model to understand the type of header information available on data frames is the International Standards Organization (ISO) 7 layer Open Systems Interconnection (OSI) model. Based on this model, header information in any (or all) layers between 1 and 7 may be present in a packet. For most switches, switching is performed based on header information belonging to OSI layers 2, 3 and 4.
Ethernet is a widely used layer 2 network protocol that uses CSMA/CD technology. An Ethernet frame has six fields. These fields include a preamble, a destination address, source address, type, data and a frame check sequence. In the case of an Ethernet frame, the switch will determine the physical path of the frame based on the destination addresses (and optionally, the class of service) of the frame. Ethernet was originally standardized at a speed of 10 Mbps—over the years various speeds of Ethernet have been standardized at rates of 100 Mbps, 1 Gbps and 10 Gbps.
A digital switch will typically have physical ports that are configured to communicate using different protocols at different data rates. For example, a blade within a switch may have certain ports that are 10 Mbit/s, or 100 Mbit/s ports. It may have other ports that conform to optical standards such as SONET and are capable of such data rates as 10 gigabits per second.
A switch fabric of suitable bandwidth is needed to transport data between source blade and destination blade.
A switch fabric is limited by its capacity to forward traffic per port and the total bandwidth or number of bits per second that can be switched without blocking or slowing the data traffic.
Traditionally, Ethernet switches have provided the highest switching capacity for a given cost. Conversely, Ethernet switches have been the lowest cost for a given switching bandwidth.
What is needed is a method and system to use a commodity Ethernet switch to function as a switch fabric in a chassis-based system.